The present invention relates to a measuring apparatus, in particular a coordinate measuring machine, comprising a first optical sensor for recording an image in an image capturing region during a first image recording time period, a first control signal transducer which provides a first control signal representing the first image recording time period, a measurement illumination arrangement for illuminating the image capturing region, a second optical sensor for recording an image in the image capturing region during a second image recording time period outside of the first image recording time period with regard to time, a second control signal transducer providing a second control signal representing the second image recording time period and comprising a control device.
The present invention further relates to a method for controlling the illumination for a measuring apparatus comprising at least two optical sensors for recording an image in an image capturing region.
Coordinate measuring machines are generally known in the prior art. They serve for checking workpieces, for example as part of quality assurance, or for ascertaining the geometry of a workpiece completely as part of what is known as “reverse engineering”. Moreover, multifarious further application possibilities are conceivable.
In coordinate measuring machines of this type, different types of sensors may be used to capture the coordinates of a workpiece to be measured. By way of example, sensors that measure in tactile fashion are known in this respect, as are sold, for example, by the applicant under the name “VAST”, “Vast XT” or “VAST XXT”. Here, the surface of the workpiece to be measured is probed with a stylus, the coordinates of said stylus in the measurement space being known at all times. Such a stylus may also be moved along the surface of a workpiece, and so a multiplicity of measurement points may be captured at set time intervals during such a measuring process within the scope of a so-called “scanning method”.
It is moreover known to use optical sensors that facilitate contactless capturing of the coordinates of a workpiece. One example of such an optical sensor is the optical sensor sold by the applicant under the name “ViScan”.
The sensors may then be used in different types of measurement constructions. One example of such a measurement construction is the product “O-Inspect” by the applicant. In an apparatus of this type, both an optical sensor and a tactile sensor are used to carry out various examination tasks on a machine and ideally with a single setup of a workpiece to be measured.
Sensor systems comprising optical sensors are becoming increasingly more important in coordinate metrology. Here, optical sensors are distinguished, in particular, by a high speed of the measuring process. In this way it is possible to carry out many examination tasks, for example in medical engineering, plastics technology, electronics and precision engineering. Various other constructions are, of course, also conceivable.
Conventionally, the optical sensor head or the optical sensor is connected to a carrier system which supports and moves the optical sensor system. Various carrier systems are known from the prior art, for example portal systems, stand systems, horizontal arm systems and arm systems, and all types of robotic systems. Here, the carrier systems may moreover comprise system components which facilitate a positioning of the sensor head which is as flexible as possible. An example for this is the articulation from the applicant sold under the name “RDS”. Moreover, various adapters for connecting the various system components of the carrier system among themselves and with the sensor system may be provided.
Moreover, it is conventional in coordinate metrology that work may be conducted with different types of illumination when measuring objects. By way of example, provision may be made of reflected light illumination which, for example, may be configured as bright field illumination or dark field illumination. The corresponding optical sensors then comprise a video camera and/or an image camera and appropriate illumination for the workpiece. Moreover, a fixed imaging optical unit is usually provided, said fixed imaging optical unit imaging the workpiece to be measured onto the camera or the optical sensors of the camera. Here, in general, provision is made of specific optical sensors comprising fixedly integrated illuminations and imaging optical units for each application or each type of measurement.
Moreover, the present invention may also find use in other measuring apparatuses, for example microscopes.
When optical measuring apparatuses are used, a user wishes to image the current measurement region or the region captured by the camera, the so-called ROI (region of interest), in the case of individual part examinations. In so doing, the ROI is visualized onto the workpiece to be measured. In the case of optical measuring apparatuses with a plurality of cameras and a single unchanging illumination for individual cameras, the ROI may either be overexposed or not properly illuminated, or dazzling effects may occur for certain camera positions, which may lead to erroneous measurements. In order to obtain an ideal measurement, different illumination settings are therefore required for the different cameras.
Various illumination control methods for optical measuring apparatuses have already been proposed in the prior art; by way of example, document DE 10 2014 208 424 A1 has proposed a method for setting the illumination of an image measuring apparatus, in which a relationship between a brightness guidance value and a current value corresponding to a brightness is calculated on the basis of a previously present relationship between a current flowing through a light-emitting device and the brightness, said method comprising the steps of creating a calibration table containing the brightness guidance value, the current value and the brightness, calculating a required brightness during a measurement, calculating a brightness guidance value corresponding to the required brightness and setting the brightness guidance value using the calibration table.
Moreover, document EP 2 078 923 A1 proposed an image measuring device comprising a camera, which ascertains images of a plurality of measurement points on the basis of a pre-set measurement procedure, and an illumination unit, which illuminates the measurement points.
Moreover, document DE 10 2014 209 471 A1 exhibits a method for controlling a part for generating a structured illumination pattern in order to illuminate a workpiece during image capturing by a camera in a specification image processing inspection system.
Under the name “Surf Max”, the applicant distributes a measuring system for scanning the surface of an object, wherein the system switches between a multitude of illuminations based on a varying position of the object. Similar measuring systems are shown in documents DE 10 2007 034 689 A1 and WO 2009/007130 A1.
Under the names “ABIS” and “ABIS II”, there is sold a measuring machine for measuring an object that switches between a multitude of illuminations. A similar measuring system is shown in documents DE 10 2007 037 812 A1 and US 2009 079 972 A1.
However, there remains a need for a measuring apparatus and a method for controlling the illumination for a measuring apparatus, which remove the disadvantages described above. It is therefore an object of the present invention to specify an improved method for controlling the illumination and a measuring apparatus, in particular a coordinate measuring machine, comprising at least two optical sensors, which provides an improved illumination of an image capturing region.